Quicktime footage SLOW RAM previews in CS5 Win7

I was wondering if anyone else is having problems with very slow RAM previews with Quicktime footage, specifically the animation and photo/motion jpeg codecs, in CS5 with Windows 7.

CS3 RAM previews this same footage on the same machine perfectly fine, and both CS3 and CS5 render normally from the render queue. CS5 will render other file types fine, but RAM previews of QT animation or photo jpeg footage in CS5 take anywhere from four to ten times as long to RAM preview as CS3.